Electric control system for condition changing devices



July 29, 1958 R. w. DE LANCEY 2,845,584

ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES Filed June 22, 1.956

7 Sheets-Sheet 1 INVENTOR PAL/ H MDELANCE ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES Filed June 22, 1956 July 29, 1958 R. w. DE LANCEY 7' Sheets-Sheet 2 INVENTOR PALPH 14/. DELA/VCEY BY 2 6% ATTORNEY July 29, 1958 R. w. DE LANCEY ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES Filed June 22, 1956 7 Sheets-Sheet 3 HHII INVENTOR RA LPH MDEL/QNCE'Y ATTGRNEY July 29, 1958 R. w. DE LANCEY 2,845,584

ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES' Filed June 22, 1956 '7 Sheets-Sheet 4 FURNACE INVENTOR L PALPH MDEA/J/vcss F BY M6.

ATTO R N EY July 29, 1958 R. w. DE LANCEY 2,84

ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES Filed June 22, 1956 7 Sheets-Sheet 5 INVENTOR RALPH MDELn/vcsv 2% j ATTORNEY y 1 1958 R. w. DE LANCEY 2,845,584

ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES Filed June 22, 1956 I 7 Sheets-Sheet 6 \Q I\ t t INVENTOR P01; 7 /4 M DEAA C Y ATTO R N EY "July 29, 1958 R. w. DE LANCEY 2,345,584

ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES 7 Sheets-Sheet 7 Filed June 22, 1956 INVENTOR PH MDZA-CEY PM. BY /f 24 06 ATTORNEY atent Ofiiice Patented July 29, 3858 ELECTRIC CONTROL SYSTEM FOR CONDITION CHANGING DEVICES Ralph W. De Lancey, Rockford, Ill., assignor to Controls Company of America, Schiller Park, Ill., a corporation of Delaware Application June 22, 1956, Serial No. 593,108

2 Claims. (Cl. 317-132) This invention relates to electric control devices and, more specifically, to a novel and improved control and electric circuit therefor useful, among other things, for operating oil-burning equipment.

The present invention is more particularly intended for use with a heating plant having a normally opencircuit room thermostat, an electrically powered fuel burner, electrical ignition means for the burner, and a furnace discharging products of combustion into a stack. It is preferably embodied in a preassembled unit having a first power supply connectible terminal, a second power supply connectible terminal also connectible to the burner and the ignition means, a third terminal connectible to the other side of both the burner and the ignition means, two terminals connectible to the thermostat, and having in its more fully developed form an additional terminal so that the ignition circuit can be made independent of the burner circuit. The unit has a normally open relay having contacts connected to the first and third terminals whereby, upon closure of the relay contact, the burner and ignition means are energized and a relay coil connected to one of the thermostatconnectible contacts, a thermally responsive reset switch having normally closed contacts and a reset switchoperating resistance heater in series with the same. It also has a cam switch having normally open contacts in parallel with the reset switch and heater, and means responsive to, predetermined rise in stack temperature for operating the cam to close the cam switch to bypass the reset switch and maintain the relay closed, and responsive to a predetermined drop in stack temperature to open the cam switch and tie-energize the relay.

A more comprehensive form of the invention includes switch means whereby the normally open contacts in parallel with the reset switch and heater may be bypassed by a high resistance circuit which holds the closed relay closed until the bypass circuit is opened, and. a still more comprehensive form separates the ignition circuit from the burner-operating circuit and provides for discontinu ing ignition after a predetermined rise in stack temperature.

Controls in accordance with the invention attain the foregoing ends and provide highly stable, dependable and low cost means that may be readily adapted to produce varied sequential actions. With reference to oil-burning equipment, the invention is directly applicable to commercial as well as residential installations, and relatively wide variations in sequential control may be obtained to meet the requirements of specific types of equipment.

Another object of the invention resides in the provision of an improved control for oil-burning and other equipment that is characterized by its simplicity, versatility and ease of adjustment and maintenance.

Still another object of the invention is the provision of an improved oil burner control and circuit therefor which will respond immediately to improper operation of the oil burner, flame failure and extinguishment, power failure and the like, to stop the burner and pre vent ignition until safe starting conditions have been re-estabiished. This is particularly important in the case of so-called gun type and other burners which atomize the fuel to secure etfcctive and efficient burning.

A further object of the invention is the provision of an improved oil burner control and circuit therefor that is compact, relatively inexpensive, and affords a high degree of sensitivity to temperature changes produced through improper or faulty operation of the oil-burning equipment.

I The above and other objects and advantages of the invention will become more apparent from the following description and accompanying drawings forming part of this application.

In the drawings:

Figure 1 is an exploded perspective view of a stack control in accordance with the invention;

Figure 2 is a front elevational view of the control of Figure l with the covers removed;

Figure 3 is a vertical cross sectional view of the control taken along the line 33 of Figure 2 and illustrates certain details of the sequence switch;

Figure 4 is an exploded view of the rotary elements of the sequence switch, the burner being shut down; I

Figure 5 is a circuit diagram of the control shown in Figures 1 through 4, the circuits being arranged for interrupted ignition;

Figures 6 through 14 illustrate the'successive positions of the sequence switch in accordance with the invention for starting and stopping an oil burner;

Figure 15 is a circuit diagram of an embodiment of p the invention arranged for continuous ignition.

While it will become more apparent as the description proceeds that the invention is generally useful for sequential control of electric circuits, the advantages, and versatility of this switch are particularly evident when considered in connection with the stack switch, or primary control, for oil-burning equipment. For this reason, the control of oil-burning equipment by means of this invention has been selected as a typical application.

One embodiment of a stack or primary control for oilburning equipment is shown in Figures 1 through 4 of the drawings, and the control is denoted generallyby the numeral 10. It includes a base member 11, a heat shield 12 spaced from the back side of the base 11, and a spirally wound thermostatic element 13 carried by and extending from the back side of the base 11. This thermostatic element has its end nearest the base 11 fixedly secured to the base, and the outer end is secured to a central shaft 14 so that the latter will be rotated'in response to changes in temperature of the element 13 when the element is disposed within the stack or other portion of the oil-burning equipment.

The front side of the base 11 is provided with a plate 15 of insulating material which carries a plurality 'of terminals 16 through 21 for connection of the control to the power supply, oil burner motor, ignition and thermostat. This panel also carries in the illustrated embodiment a transformer 22 a, reset switch 23, a sequence switch 24, and a relay 25. The reset switch 23, as will be explained in connection with the circuit diagram, includes a bimetallic member and an associated heating element. The reset switch responds to interrupt burner operation in the event it is not by passed by the sequence switch 24 when the latter is operated in response to heating of the spiral thermostatic element 13. The sequence switch is shown and will be described more specifically in connection with Figures 3, 4 and 6 through 14, inclusive.

For a detailed description of the reset switch 23, reference is made to 'applicationfor U. S. patent, Serial No. 603,268, filed August 10, 1956, entitled Electrical Switches.

A bracket 26 extending forwardly of the bottom side of the base 11 has several openings 26 therein to receive and hold the electric Wiring forattachment to the terminals 16 through 21, inclusive.

The elements mounted on the panel 15 of a control are enclosed by a cover 27 of insulating material having an opening 27 to'receive the shaft 34 of the sequence switch 24. When the cover 27 is in place on'the base 11, a knob 28 is securely fastened to the end of the shaft 34 of the sequence switch 24. The cover 27, while enclosing the operating parts of'a control, does not cover the terminals 16 through 21. The front face carries diagrammatic wiring directions in order to facilitate connection of the control to the external wiring. A second cover 29 encloses the cover 27 as'well as the terminals 16 through 21, inclusive. It is secured to the base by means of screws 30 cooperating with slots 31 in the cover. In addition, both of the covers 27 and 29 include openings 32 and 33. The shaft 23 of the reset switch 23 extends forwardly of the outer cover so that the switch may be reset without the removal of either of the covers 27 and 29.

The sequence switch 24 is operated in response to rtation of the shaft 14 produced by heating and cooling of the thermostatic element 13. As shown in Figures 3 and 4, the flat shaft 14 enters a correspondingly shaped socket 34 'of the'shaft 34 of the sequence switch 24. A pair of cams 35 and 36 are rotatably mounted on shaft 34. The outer end of this shaft carries the knob 28 previously described. A clutch 37 is frictionally coupled with the shaft 34 and is provided with a pair of outwardly extending studs 38 for engagement with openings or depressions 39 in one face of the cam 35. Operation of the cam 35 is therefore accomplished in response to rotation of the shaft 14, and the degree of rotation in each direction is limited by suitable stop means 81, il-

lustrated in Figures 6 through 14. The cam 36 is retated in response to rotation of the cam 35 by means of an outwardly extending key or pin 40 on one side of the cam 35 and a cooperating slot 41 in cam 36. The key 01 pin 40 is made somewhat smaller than the width of the slot 41 in order to shift the phasing of the cams upon reversal of rotation. The assembly of these several elements of the sequence switch is shown in Figure 3, and

a more detailed description willbe found in my application, Serial No. 560,652, filed January 23, 1956, entitled Electrical Switches.

The electrical switch means operated by the cams 35 and 36 include cooperating switch elements 42, 43 and 44, 45 associated with the cam 35, and switch elements 46, 47 and 48, 49 associated with the cam 36. By reason of the slip clutch 37 and the pressure of the switching elements on the cams 35 and 36, the rotation of the shaft 14 required to effect complete sequence of 0peration of the switches first in one direction and then the other can be controlled by the frictional cooperation of the clutch 37 with the shaft 4. By reducing the friction between the clutch 37 and the shaft 34, the angular rotation of the shaft 14 required to effect complete cycling of the switch is decreased, while increasing the friction will increase the rotation required for such cycle. it follows from the above-that when the thermal change required for complete cycling of theswitch is to be decreased the clutching force must be decreased and that when the thermal changerequired for such cycling isto be increased the clutching forcemust also be increased.

The sensitivity of the control to temperature changes may therefore be varied in this way. In addition, the stop 81 associated with cam 35 also functions to vary the response of the control to temperature changesas will be pointed out in connection with Figures'6'through 14.

shown diagrammatically in Figure 5 and includes, in ad- Referring now to Figure 5, illustrating a circuit in accordance with one embodiment of the invention, the earns 35 and 36 are shown in their counter-clockwise position, which is the position assumed when the oil-burn ing equipment is shut down. Under this condition, the switch contacts 42, 43 are open while contacts 44, 45 on cam 35 and contacts 46, 47 and 48, 49 on cam 36 areclosed.

Power for the operation of the control as well as the oil-burning equipment is applied to terminals 16 and 17 of the control through a master control switch .50, a. suitable fuse 51, and a secondary control .switch 52, the latter usually being positioned at a readily accessible place for turning off the entire system in the event of an emergency. The transformer 22 provides low voltage for the thermostat circuit, which includes, among other elements, thermostat 53 and relay 25. The primary 54 of this transformer is connected through leads 55 and 56 directly to the terminals 16 and 17.

The control circuit for starting and stopping the oil burner 57 mounted in a suitable furnace 58, as illustrated, includes the thermostat 53, thermostat terminal 21, the lead 59, the secondary 60 of the transformer 22, the lead 61 to the coil 62 of relay 25, leads 63 and 64, sequence switch contacts 44 and 45, lead 65, heating element 66 of the reset switch 23, contacts 67 and 68 .of

the reset switch, and lead 69 to the thermostat terminal -20. When the burner is in the normal shut-down condition, this circuit is completed by closure of the contacts and 18, energy is supplied to the motor 76, which functions to deliver both oil and air to the burner. In addition, the ignition means 79 is connected to terminals 17 and 19 by leads 79a and 79b and therefore is also energized to ignite the air and oil mixture.

Before discussing further details and operation of the circuit of Figure 5, reference is made to the reset switch 23,"which cooperates with the other elements of the circuit" to provide certain safety features. This switch .is

dition to the contacts 67 and 68, a bimetallic element 80 that functions to open and close the contacts 67 and 68 in response to heat generated by the resistor 66. The

contacts 67 and 68 are, as previously described,.in series with the control circuit, including the thermostat 53, and

should the burner fail to ignite and generate heat within a :predetermined time determined by the characteristics of the bimetallic element 80 and the resistor 66, flexing of the bimetallic element 80 will cause the contacts 67 and 68 to open and thus turn off the burner. While not illustrated in Figure 5, the reset switch 23 includes means to hold the contacts in the open position when actuated by the element 80, and means in the form of a manually operated push button 23' (see Figure 1) is provided in order to close the contacts to reset the control.

When the burner has completed a cycle and the. stack has cooled, or when the cam' switch has been reset by knob 28, the cams 35 and 36 are in the positions illustrated in Figure 5. In this position, the contacts 42 and 43 are in the open position while the other three sets of contacts are closed. This is the normal starting position for the sequence switch 24 and, inasmuch as the cams are frictionally coupled to the bimetallic element 13, these cams are preset by rotating the knob 28 to the left, as

viewed inFigure' 1, to automatically phase the cams with stack of the furnace to impart clockwise motion to the cams 35 and 36, as viewed in Figure 5.

The operation of the earns 35 and 36 when moving from the start position of Figure 5 to the run position is illustrated in Figures 6 through 10, inclusive. It will be observed that the position of the cams in Figure 6 is identical to that in Figure 5, and a stop member 81 associated with the cam 35 limits both clockwise and counterclockwise rotation. As the bimetallic element 13 responds to heat generated by combustion of the fuel, the cams will rotate to the position shown in Figure 7. In this case, the contacts 44 and 45 have opened to break the starting circuit through the reset switch 23.

However, the contacts 48 and 49 on the cam 36, together with a series resistor 82, form a bypass circuit which includes the lead 83 from contact 45 to contact 49, a lead 84 from the contact 48 to the resistor 82, and a lead 85 from the resistor 82 to the contact 67 of the reset switch 23. When contacts 44 and 45 are opened, the resistance inserted in series with the starting circuit reduces the current in that circuit to a point sufficient to maintain the contacts of relay 25 in the closed position but insufiicient to cause the relay contacts to reclose should power he momentarily interrupted. Thus, complete protection is alforded against reignition after flameout due to any cause until safe starting conditions are reestablished.

Assuming, as is normally the case, that the power is continuously supplied to the control circuits, cam 35 is moved by the element 13 to the position shown in Figure 8. It will be observed that the pin 40 on cam 35' has now moved within the slot 41 of cam 36 so that it contacts the clockwise edge 41' of that slot. Up to this point, no rotary motion has been imparted to the cam 36, but contacts 42 and 43 of cam 35 are now closed. These contacts are connected in parallel with the contacts 48 and 49 by means of the leads 64 and 83, coupling the contact 42 with the contact 49, and leads 86 and 84, coupling the contacts 43 and 48. Continued rotation of the sequence switch causes both of the cams 35 and 36 to move to the position shown in Figure 9. In this position, the contacts 46, 47 and 48, 49 associated with the cam 36 are in the process of opening, and the cam 35 approaches the stop 81, which limits its rotation in a clockwise direction.

During the starting period, the contacts 46 and 47 have been closed to supply ignition to the burner. As combustion has continued for a substantial period, ignition is no longer required. Due to the configuration of the parts, the opening of the contacts associated with the cam 36 imparts rotary motion to the cam 36 to advance its position relative to the cam 35, as shown in Figure of the drawings. In this position, it will be noted that the pin 40 has moved toward and may even be against the counter-clockwise edge 41" of the slot 41 of the cam 36. In addition, the cam 35 is moved clockwise into engagement with the stop 81, and contacts 42 and 43 are closed, while all of the other contacts are open. This position is called the run position of the cycle.

After the demand for heat has been satisfied, the contacts on thermostat 53 open to de-energize the relay 23 and cause its contacts 70 and 71 to open and disconnect power from the oil burner. As the bimetallic element 13 cools after combustion has been interrupted, the cams 35 and 36 are moved in a counter-clockwise direction as shown in Figures 11 through 14, inclusive. Since the pin 40 of cam 35 is against, or soon will bear against, the counter-clockwise edge 41" of the slot 41 of cam 36, both cams move simultaneously in the counter-clockwise direction. Movement of the cam 35 functions to open the run contacts 42 and 43, as shown in Figure 11, so that at this stage, all of the contacts are open. Continued rotation of the cams causes the cam 36 to close its associated contacts 46, 47 and 48, 49, as shown in Figures 12 and 13,

6 while the contacts associated with the cam are still in the open position. When the cam 35 moves against the stop 81, it has come to the position shown at Figure 14, and the contacts 42 and 43 are opened, while all other contacts are closed. The cams are now in a start position identical to that shown in Figures 5 and 6.

It will be observed in connection with the control circuit, that the reset switch contacts 67 and 68 are not bypassed at any time by other control switches. Thus in starting the burner, contacts 67 and 68 completely controi its operation; failure, for example, of contacts 42 and 43 to close properly after the burner has started will nevertheless result in a complete interruption of burner operation.

Another advantage of the reset switch resides in the utilization of a negative temperature coefficient resistor as resistor 66. By properly coordinating the value of resistor 66 with resistor 82 at ambient temperature, the initial current through relay coil 62 can be maintained slightly below the critical value for pull-in of the relay. However, the heat produced in resistor 66 will lower its resistance and the current through the relay coil will gradually increase to and beyond the critical operating value and close the relay. Thus an automatic delay is interposed in the operation of the burner and avoids possible damage to the equipment by a rapid and repeated making and breaking of the control circuit often produced by the chattering of thermostat control contacts.

The utilization of NTC resistor 66 offers still another advantage, namely, protection of the control and burner against excessively high line voltages. For instance, should the line voltage be excessively high, a proportional increase in current will flow through the relay control circuit. However, in view of the relatively high cold value of resistor 66, the resistor 82 will not pass suflicient current to operate the relay alone and the increased rate of heat generation by resistor 66 can be utilized to open the reset switch contacts 6768 before contacts 44 and 45 open in the normal start cycle.

It will be observed from the foregoing description that the operation of the sequence switch 24 is brought about by relative temperature changes in the furnace or stack temperature irrespective of the actual temperature. Through the adjustment of the pressure of the contacts on their associated cams, and through the friction of the clutch and the position of the stop 81, with reference to the cam 35, the change in temperature required for the operation of the switch can be adjusted to any de sired value. In normal cases, a temperature change of about degrees Fahrenheit has been found to be highly satisfactory.

In certain applications, it may be desirable to use the control shown in Figure 5 with a so-called high voltage control circuit. In this case, the thermostat 53 would be arranged to operate at the line voltage, and the relay 25 would include a coil 62, also operable at the line voltage. Leads 61 and 59 would be directly connected to the leads 56 and 55, respectively. Transformer 22 is then omitted.

A further embodiment of the invention is shown in Figure 15 of the drawings. Under certain conditions, it is often desirable to maintain continuous ignition throughout the run period of the burner. To attain this end, the contacts 46 and 47 on cam 36 are eliminated, and the lead from the ignition means 79 to the terminal 19 is moved to the terminal 18, and the terminal 19, together with the leads 74 and 75 as shown in Figure 5, are removed. The operation of the cams 35 and 36, as well as the other elements of the circuit, remains unchanged so that the operation of the control, as described in connection with Figures 5 through 14, is directly applicable. With the circuit of Figure 15, the ignition is started upon the initial closure of the contacts of thermostat 53 and continues to operate until the thermostat contacts are opened to turn otf the burner. If desired, the control circuit of Figure 15 may be operated at volts or line 7 voltage, inthe. same manner asdescribed in connection with Figure 5, through the elimination of the transformer 22san'd themodification of 'thethermostat 53 and relay 25.

While only certain embodiments of the invention have been illustrated and described, it is apparent that modifications, alterations and changes may be made without departingfrom the true scope and spirit thereof as defined in'the appended claims.

What isclaimed is:

1. In an electrical control for operating electrical equipment in response to changes in a condition compris ing' a relay for controlling the operation of said equipment, a relay control circuit including series connected power source terminals, switch means responsive to said condition and a first resistor, a reset switch having a pair of contacts connected to make, and break said control circuit, a bimetallic element holding the last said contacts in the closed position and a negative temperature coeflicient resistor effectively connected in parallel with said -first resistor for heating said element toopen the last said contacts, the combined resistance of both said resistors at ambient temperature beingsufiicient to limit the initial relay current slightly below the critical value for pull-in of said relay, andswitch means adapted to be responsive to normal operation of said equipment and connected with said negative temperature coeflicient resistor for interrupting the current therethrough. I

2. Inan electrical circuit according to claim 1 in which saidfirst resistor has a value that will provide suflicient holding current for said relay upon interruption of the current through said negative temperature coefiicient resistor.

References Cited in the-file of this patent UNITED STATES PATENTS 1,636,191 McCabe July 19, 1927 2,157,710 Lake May 9, 1939 2,217,886 Book Oct. 15, 1940 2,720,254 Ward Oct. ll, 1955 Bishofberger Oct. 11, 1955 

